SU1206850A1 - Electric contact for vacuum circuit breaker - Google Patents

Description

The invention relates to low voltage electrical apparatus, in particular, vacuum arc suppressing chambers (VDC) embedded in switching devices, such as vacuum circuit breakers.

The aim of the invention is to increase the switching resistance of the contact.

The drawing shows the proposed electrical contact.

The electrical contact consists of a refractory lining 1, an exaggerated glass-shaped, and a low-melting alloy 2, which fills the cavity with a refractory lining. The outer surface of the bottom 3 of the refractory lining fulfills the function of the working contact surface. The brass surface 1 is securely fixed to the end face of the electrode 4. In the bottom 3, the through holes 5 are filled, the Fusible alloy 2 through the holes 5 goes to the working contact surface flush with it.

Due to the refractory lining of the glass-shaped, a large mass of low-melting alloy can be put in contact, which contributes to higher switching durability. The outflow or extrusion of a fusible alloy from the cavity is prevented by the bottom of a refractory alloy; Depending on the rated current, voltage, and other technical parameters of the vacuum switch, the optimal parameters of the refractory contact pad are chosen to ensure maximum contact performance. The ratio of contact height H and cavity height h occupied by a low-melting alloy in the range 0.33-h / f $ 0, 6, taking into account the necessary contact diameters, as well as

contact material, allows reach-.,. Spare holes on the refractory impose a stable switching durability of at least 6-7 million cycles.

The design of the contact pad allows to perform a cavity occupied by a low-melting alloy with a height of at least 7 mm, without disturbing (leaking the low-melting alloy) the work of the contacts, as well as using the entire low-melting alloy embedded in the cavity.

If contacts between them diverge, an arc or several arcs burning in the metal vapors arise. 50

Ke significantly affects the switching durability of the contact.

At the contacts, satisfactory switching durability is achieved if the total area of the holes is 25-30% of the outer diameter of the refractory lining. Increasing this area reduces the contact area of the contacts by narrowing the necks of the refractory lining between the holes, t, e. areas of current flow, which reduces the switching resistance of the contacts.

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The arcs move along the working surface of the bottom of the glass-like lining, heat the fusible alloy, as a result of which the latter melts and intensively begins to evaporate. The droplets of the molten low-melting alloy rise up, some of them exit through the holes to the working contact surface and evaporate, the other part lingers on the inner surface of the bottom and the machines of the refractory glass-like lining. When current passes through the zero, the arc is replaced by a zone of high electrical strength, while the contacts are cooled, unburned metal vapors, settle down, solidify on the working contact surface of the bottom and the walls of the refractory lining and can be used for the subsequent burning of the arc. up to complete burnout fusible alloy.

The holes made in the bottom of the fusible lining provide the exit of the low-melting alloy to the working contact surface. The size of the holes depends on the fluidity of the low-melting alloy 2 and on the permissible switching capacity. The diameter of the holes must be so different, the greater the fluidity of the alloy and the required switching capacity. It is preferable to make holes with a diameter of 8-10% of the diameter of the refractory lining (taking into account that the diameter of the refractory lining is usually made up to 50 mm. Holes with a diameter less than 8% of the diameter of the contact strip are not economically profitable, and a diameter of holes of 10% above can lead to falling softened alloy.The choice of the diameter of the holes, as well as the total

Ke significantly affects the switching durability of the contact.

At the contacts, satisfactory switching durability is achieved if the total area of the holes is 25-30% of the outer diameter of the refractory lining. Increasing this area reduces the contact area of the contacts by narrowing the necks of the refractory lining between the holes, t, e. areas of current flow, which reduces the switching resistance of the contacts.

Claims (1)

ELECTRICAL CONTACT FOR A VACUUM CIRCUIT BREAKER, consisting of a refractory plate fixed to the contact holder with cavities filled with a low-melting alloy, with a joint in that, in order to increase switching wear resistance, the refractory plate is made in the form of a glass with through holes in the bottom and mounted on the contact holder upside down.